The present invention relates to a process for preparing a preferred iron humate product, compositions of preferred iron humate products and a method for treating chlorosis in vegetation using preferred iron humate products.
Many agricultural crops and turf grasses must have commercial applications of iron nutrients in order to prevent or correct for iron deficiency otherwise known as plant chlorosis. Chlorosis can be physically detected by yellowing of leaves in trees, shrubs, and vegetables and yellowing of blades within turf grasses. Chlorosis hinders plant growth or yields and can also lessen food quality. Additionally, many soils are deficient in organic substances which can have a favorable effect on soil moisture retention, plant nutrient uptake and plant growth. There are many commercial iron nutrient sources available to correct for iron chlorosis such as ferrous sulfate and chelated irons such as sodium ferric ethylenediamine di-(0-hydroxy-phenol-acetate)("FeEDDHA") sold under the trade names Sequesterene 138-Fe and Libfer SP.
A separate problem has been the disposal of sludge or precipitates formed by coagulating raw water contaminants with iron and aluminum salts or the like at potable water treatment plants and at plants designed to remove the organic color from effluents from such sources as paper mills. This is especially true for surface waters which are characterized by their high content of dissolved organic color from the natural decaying of aquatic vegetation. These potable water treatment plants must use high coagulant dosages, which in turn, generate large quantities of sludge residue for disposal. Often the water treatment sludges are simply dumped back into the water source causing degradation of the water quality. Other currently preferred options for disposal of water treatment sludges are lagoon storage, disposal in landfills and discharge into sanitary sewers. Inadequacies in these disposal methods has led to an increased interest in the land application of water treatment sludge.
Important constituents of natural surface waters are aquatic humic substances. Humic substances are formed from the decomposition of plant and animal materials and comprise the largest fraction of natural organic matter in natural surface waters accounting for 40 to 60 percent of the dissolved organic carbon ("DOC"; DOC is defined as organic carbon particles smaller than 0.45 micrometers in diameter and may be in colloidal suspension rather than in solution).
Humic substances comprise a complex heterogeneous mixture of compounds that are not readily separated into discrete components. However, three subfractions of humic substances are generally recognized. These subfractions comprise humic acid, fulvic acid and humin. Humic acid is defined as the fraction of humic substances that is not soluble in water under highly acidic Conditions (pH&lt;2.0) but is soluble at higher pH values. Fulvic acid is defined as the fraction of humic substances that is soluble in water under all pH conditions. Humin is defined as the fraction of humic substances that is not soluble in water at any pH value.
Humic substances are removed from raw drinking water due to several problems associated with their presence. Humic substances are responsible for the yellow or brown organic color of natural surface waters. Humic substances act as a vehicle for the transport of toxic, water insoluble elements and organic micropollutants. Chlorine combines with aquatic humic substances to form chlorinated organic compounds, such as chloroform and complex chlorinated compounds, that may have negative effects on health. Humic substances also precipitate in water distribution systems where they lead to deterioration of tap water quality and increase the need for interior cleaning of pipes.
Traditionally, colored surface waters have been treated with alum (aluminum sulfate) which generates an aluminum containing sludge, which after dewatering, must be deposited in a secure landfill. Iron salt coagulants have been effectively used but often produce a sludge high in heavy metals due to the quality of the iron salt coagulant. Many of the commercial iron salt coagulants are produced from by-products from such sources as TiO.sub.2 production or steel pickling and are typically high in heavy metals and organic contaminants.
When an iron salt coagulant is used as the primary coagulant to remove humic substances, it reacts to precipitate an iron humate residue. The inferior quality of many iron salt coagulants, in terms of concentration of heavy metal contaminants, often results in iron humate products having unacceptable concentrations of heavy metals so as to prevent land application of the iron humate products.
Another problem with current potable water treatment methods is that these methods generally result in a water treatment sludge having unnecessarily high concentrations of hydrous metal oxides, such as iron hydroxides. Hydrous metal oxides are strong adsorbents of trace metals and phosphorus. When applied to the soil surrounding vegetation at high concentrations and high pH, iron hydroxides can result in metal deficiencies in the vegetation including iron deficiency. Also the presence of hydrous metal oxides results in the sorption of phosphorous from the soil reducing the availability of phosphorus to vegetation. Phosphorous is necessary for vegetation growth. Additionally, iron hydroxides do not dewater as well as iron humate products. The iron hydroxides form a somewhat gelatinous mass making sludge containing excess iron hydroxides harder to handle and more expensive to transport.